1. Field of the Invention
The invention relates to apparatus and methods for comparing and correlating disparate types of data and providing a combined presentation of the data to aid in the diagnosis of biological disorders.
2. Background of the Related Art
Frequently medical doctors and technicians attempt to diagnosis a biological disorder of a patient using the results of several different types of tests. This often requires that two or more disparate types of data be correlated and/or compared to one another to determine the cause of a biological disorder or condition. Correlating and/or comparing the disparate types of data can be difficult and time consuming because the disparate types of data are often presented in different formats or in different orientations.
For instance, when a doctor is attempting to determine why a patient has lost some degree of vision sensitivity, he will usually begin by conducting a perimetry test, which determines which areas within a patient's visual field have experienced a loss of sensitivity. The doctor will then attempt to match up a loss of vision sensitivity to a specific eye disorder or biological defect. The eye disorder or biological defect must be determined by examining the biological structures responsible for vision using some sort of testing device. The doctor must then compare and correlate the perimetry data to the data on the biological structures to determine whether a defect or condition of a biological structure is responsible for a measured loss of vision. This comparison is often difficult because of the very different ways that perimetry data and biological structure data are presented, as will be explained below.
Perimetry testing, which measures the sensitivity of a patient's eye, can be done many different ways. The results of a perimetry test are presented on a chart that is indicates the sensitivity of one or more eyes at different positions within the eye's visual field. Regardless of the method used, the results are usually presented in one of two different formats.
The results of a perimetry test are shown in a first format in FIG. 1. A plurality of concentric isopter lines 22, 24, 26, 29 are drawn on the chart to indicate the eye's sensitivity. Each isopter line connects points within the patient's visual field having substantially the same sensitivity. The isopter line 22 corresponds to the lowest visual sensitivity, whereas isopter line 29 corresponds to the greatest optical sensitivity. The isopter lines provide a map of how the sensitivity of the patient's vision changes within the field of view.
As can be noted from the chart 20 in FIG. 1, the sensitivity of a person's vision does not vary in a simple proportional manner as one progresses from the center of the line of vision outward towards the fringes of the patient's peripheral vision. In addition, because of the structure of the human eye, a patient's field of vision through an individual eye will always include a blind spot 28 located to the temporal side of the central line of vision. The blind spot 28 corresponds to the point on a person's retina at which the optic nerve is attached.
Perimetry testing is performed on each of a patient's eyes, individually. A chart such as the one shown in FIG. 1 represents the sensitivity of a person's vision through a single eye. However, it is common to present the results of perimetry testing in a chart such as the one shown in FIG. 2, which shows the sensitivity of a person's vision in both the left and the right eyes.
The chart shown in FIG. 2 is arranged such that the left hand side of the chart corresponds to the patient's vision through his left eye and the right side of the chart corresponds to the patient's vision through his right eye. This orientation is referred to as a "patient's view" orientation. This means that the information corresponding to the left and right eyes are oriented on the page such that they correspond to how a patient would see out into the world.
Perimetry data is presented in a different format in the chart shown in FIG. 3. This chart, which includes a plurality of numbers arranged on perpendicular axes, also indicates a patient's visual sensitivity at different positions within the visual field. The greater the number, the greater the patient's sensitivity at a particular location. The perimetry chart in FIG. 3, like the one in FIG. 2, is arranged in a "patient view" orientation, where the left side represents the visual sensitivity of the patient's left eye and the right side represents the visual sensitivity of the patient's right eye.
As can be seen for the left eye in the chart of FIG. 3, the numerals towards the center of the patient's vision are in the low to mid 30's while the numerals at the edge of the person's vision tend to be in the mid 20's. This indicates that the patient's vision is more sensitive toward the center of his field of vision, and less sensitive toward the edges of his field of view.
Perimetry charts such as the ones shown in FIGS. 2 and 3 indicate the sensitivity of photo-receptors located on the retina of a patient's eye. For a single eye, the sensitivity indicated on the left side of a perimetry chart actually corresponds to photo-receptors located on the right side of the retina. Similarly, the sensitivities indicated on the top of a perimetry chart correspond to photo-receptors located on the bottom of the retina. The inversion of the sensitivity information relative to the location of the photo-receptors is caused by the lens of the eye, which inverts images that pass through the lens. FIG. 4 is a diagram helpful in understanding the inversion of images. The lens 70 of an eye will invert an image 74 as the image is focused on the retina of the eye. The focused image 72 is upside down and is reversed from left to right relative to the original image 74.
A doctor examining a patient's eye will typically look into the patient's eye using a magnifying device to conduct a visual examination of the transparent structures of the eye. To accomplish this examination, light from an instrument is typically beamed into a person's eye, and the light reflects off the structures of the eye, back through the lens 70 of the eye, towards the doctor. Because of the eye's lens 70, the image of the structures leaving the patient's eye is inverted with respect to the location of the actual structures. Some devices that allow a doctor to perform such an examination will simply magnify the image that passes through the lens. Thus, the doctor is viewing an inverted image of the eye structure. Other devices that allow a doctor to conduct such an examination will automatically invert the image that emerged from the lens so that the image of the structures seen by the doctor are correctly oriented relative to the actual structures.
An image of the visible structures of an eye is typically called a fundus image. An example of a fundus image is shown in FIG. 5. A fundus image will usually show the retina of the eye and visible blood vessels. The point at which the optic nerve attaches to the retina usually appears as a lighter area in the image. A portion of the eye called the macula (which corresponds to the center of an eye's field of vision) will usually appear as a darker area in the image.
There are several different types of devices which can record a fundus image of the visible structures of an eye. These devices can record a photographic image of an eye's structure, or they can utilize a charge coupled device to record electronic data corresponding to an image of the eye's structure.
When fundus images of a person's eye are presented, they are typically presented as shown in FIG. 6. The right eye is typically shown on the left hand side of the page, while the left eye is shown on the right hand side of the page. This orientation is called the "doctor view" orientation. Because the devices that obtain fundus images of a person's eye will typically automatically invert the image that passes through the lens of an eye, structures shown at the top of a fundus image correspond to structures actually located at the top of the eye. Similarly, structures appearing on the right hand side of the fundus image correspond to structures actually located on the right side of the eye.
Unfortunately, a doctor may find it difficult to correlate a loss of vision shown in perimetry chart, such as the ones shown in FIGS. 2 and 3, with the structures shown in a fundus image, such as the one shown in FIG. 6, due to the orientations of the information appearing on a perimetry chart and orientations of the eye structure shown in a fundus image. This difficulty is caused by the presentation of perimetry data in a "patient view" orientation and the presentation of fundus images in a "doctor view" format. The relative positions of the left and right eyes in a fundus image are reversed with respect to the positions of the left and right eyes on a perimetry chart. In addition, due to the inverting effect of the eye's lens, a loss of vision sensitivity indicated at the top portion of a perimetry chart actually corresponds to a loss of sensory ability of the structures located at the bottom of a person's eye. Thus, the information shown in a perimetry chart is actually inverted top-to-bottom and left-to-right with respect to the structures shown in a fundus image. Because the orientation of the data on a perimetry chart is inverted with respect to the structures shown in a fundus image, a doctor can have difficulty relating the information in a perimetry chart to the structures shown in a fundus image. This makes the diagnosis of eye vision disorders difficult and time consuming.
The same types of problems are encountered when other disparate types of test data must be correlated to diagnose a biological disorder or condition.